This invention relates to a method for forming a dresser pad for chemical mechanical polishing, especially about a method for forming a dresser of a diamond abrasive wheel.
In recent years, each integrated circuit company must be decreasing running cost and increasing product competitiveness by increasing the packing density of integrated circuits. To increase the packing density of integrated circuits, not only must the component size be decreased, the distance between components also must be shortened. Recently the rapid development of chemical mechanical polishing (CMP) has become the key technology of rapid increasing of integrated circuit packing density.
The CMP usually places a polishing pad on the circular polishing table, then uses a wafer carrier to press the wafer on the polishing pad with slurry to reach the CMP effect by relative motion between the wafer and the polishing pad.
The polishing pad is composed of blown polyurethane and lubricated by slurry. The production process of using the polishing pad assembly on the CMP machine and the assembly process is labor-consuming. All of the polishing pad cost, the labor cost of polishing pad assembly on the CMP machine and the production loss during the assembly process increases the CMP cost.
The main reason for polishing pad wear is the smoothing phenomenon, that is, during the CMP process, the polishing grains in the slurry and by-product of polishing will be buried in and block the holes of polishing pad. The smoothing will decrease the polishing rate; and make the polishing time and degree not easily controlled. To overcome the smoothing problem, the polishing pad has to be pruned periodically to remove the buried polishing grains and by-products in the pad. The present pruning technique includes liquid rinsing, gas blowing and polishing pad. The polishing pad effect is the best. A polishing pad dresser on the CMP machine uses a rotating diamond abrasive wheel to prune the polishing pad. The smoothing problem is expected to be overcome after pruning to increase the CMP polishing rate.
There are two methods to form the aforesaid diamond abrasive wheel on the polishing pad dresser: electrical plating and sintering. During the plating process, the diamond is joined with welding material by physical bonding. Since the diamond itself doesn""t conduct, it will hinder the welding material from being plated on the joint of the diamond and the welding material surface so there will be a concavity on the joint and the grab strength will be decreased. Therefore, the diamond abrasive wheel formed by plating is not suitable for the CMP pad dresser.
In the sintering process, the welding material like copper, silver and some active metals like titanium is sprayed or green printed on the polishing pad dresser to form a sintering layer, then the diamond grains are randomly distributed on the sintering layer prior to feeding it into the high temperature sintering stove. In the conventional sintering process, the density and uniformity of diamond distribution and the ratio of diamond grain exposure cannot be precisely controlled. So the polishing pad dresser made by conventional technology has poor pruning effect on the CMP pad; the uniformity is not stable and hard to be controlled.
To increase the CMP pad quality and life, the polishing rate, the uniformity and stability of polishing pad dresser has to be precisely controlled.
The main object of this invention is to provide a method for forming a dresser pad for chemical mechanical polishing.
It""s another object of this invention to provide a method for forming diamond abrasive wheel on CMP pad dresser.
It""s still another object of this invention to prvide a chemical mechanical polishing pad dresser.
The process of this invention includes production of the bottom seat, then checking the bottom seat. If the bottom seat matches specification, then proceeding to the pre-process of the bottom seat. Then preparing a welding metal powder and organic glue, mixing the welding metal powder, organic glue and an adequate ratio of water to form a thick welding liquid, and using screen printing, spraying or other film production technology to uniformly distribute or paste on the aforesaid dresser bottom seat to form a sintering layer. Then, the computer visual inspection system is used to uniformly distribute the sieved diamond grains on the sintering surface, and after diamond peak planarization process, the aforesaid dresser is placed in the high temperature stove, and sintered in a vacuum environment, a protection atmosphere or a hydrogen stove to make the CMP pad dresser.
After sintering in the high temperature stove, the flatness of the dresser has to be checked. Then the real test is conducted to make sure of the polishing function of the formed dresser.